Convert volumetric flow rate between GPM, litres per second, cubic metres per hour, CFM and more — enter one value and read it in every unit at once.
One Flow, Many Units
Flow rate is a volume per unit time, and almost every trade measures it differently: plumbers in gallons per minute, process engineers in litres per second or cubic metres per hour, and HVAC in cubic feet per minute. They all describe the same thing, and converting between them is just a matter of consistent factors.
| Equivalent | Value |
|---|---|
| 1 US GPM | 3.785 L/min = 0.0631 L/s |
| 1 L/s | 15.85 US GPM = 3.6 m3/h |
| 1 CFM | 0.4719 L/s = 1.699 m3/h |
| 1 m3/h | 4.403 US GPM |
Frequently Asked Questions
Is this US or Imperial gallons?
US gallons. One US gallon is about 3.785 litres; an Imperial gallon is about 4.546 litres, so UK GPM figures run roughly 20 percent higher.
What is CFM used for?
Cubic feet per minute is the common unit for air and gas flow in HVAC and compressed-air work, where liquids are usually metered in GPM or L/s.
Does flow rate depend on pipe size?
The volumetric rate does not, but velocity does – the same GPM through a smaller pipe means higher velocity and more friction loss.
Related calculators
- Pipe Flow Calculator — velocity and flow in a pipe.
- Pressure Drop Calculator — friction loss at a given flow.
- Engineering Unit Converter — the all-in-one converter.